Manufacture of aluminum chloride



July 19, 1932. A. MCD. MGAFEE Y MANUFACTURE 0F ALUMINUM CHLOHCIDEV A Filed Sept. 30. 192'? Maggi;

Patented July 19, 1932 UNITED STATES i PATENT OFFICE LEER MCDUFFIE MCAFEE, OF PORT ARTHUR, TEXAS, ASSIGNOR T0 GULF REFINING COMPANY, 0F PITTSBURGH, PENNSYLVANIA, A CORPORATION OF TEXAS murac'ruaa or ALUMINUM cnroamn .Application led September 30, 1927. Serial No. 228.068.

This invention relates to the manufacture of aluminum chloride; and it comprises a process of making aluminum chloride wherein a fine grained mixture of alumina, such as bauxite, and carbon, such as oil coke, is projected in aerial suspension by a jet of chlorin containing enough admixed oxygen to cause a quick and energetic development of heat at the expense of some of the carbon, the projected materials forming what may be called a ame burning in fr ee suspension with the solids and chlorin vanishing entirely therewithin; combustion and reaction being usually regulated by employing a small proportion of diluent gas with said oxygen; all as more fully hereinafter set forth and as claimed.

In the accepted method of making anhydrous aluminum chloride, hot carbon and alumina are subjected to the action of chlorin. The alumina is ordinarily employed in the form of bauxite. On mixing bauxite with carbon and subjecting it to the action of chlorin at a temperature of 1600 F., or higher, all the components are chlorinated, producing a mixture of chlorides in the vapor form; aluminum chloride being the major component. .If the conditions of operationl are correct, neither chlorin nor solid matter will remain. For efficient operation everything should be dry and free of hydrogen to prevent waste of chlorin as HC1 and no more than a trace of free chlorin should remain with the vapors. The operation, however, in

ractice requires a considerable amount of eat to keep it going and it goes forward most smoothly at a temperature around 2000 F. 'Temperatures above 2800 F., and especiall with impure bauxite, are sometimes disa vantageous because of clinkering or sintering retarding the actions.

All methods now in use however suffer from apparatus diiculties and are, moreover, relatively slow it being diilicult to gain, high capacity without apparatus of inordinate size. Apparatus diiculties are inherent wherever hot carbon and chlorin come into contact with chamber walls of cla or the ordinary ceramic materials. Firebrlck linings are shortlived.

In the prior art, propositions have been made to escape these difficulties with the walls of the reaction chambers by performing the whole reaction with the-materials in aerial suspension. In principle this suggestion is sound but diliculties lie in its application. If, as has been proposed, the entire heat necessary is furnished by preheat of the chlorin, coke and bauxite, there is trouble in controlling condition so as to have neither bauxite nor chlorin lpass forward unutilized; and moreover pre eating chlorin is not a convenient operation. If a certain amount of air is mixed with the rojected solids and chlorin,

there is the fpr uction ofa liame and heat or r is supplied eaction within the flame itself; but the difiiculty is found of slow and irregular action. rl`he time afforded for reaction within the flame is not suilicient. to give complete utilization of the chlorin and bauxite; `this being probably due to mechanical hindrance by thediluting nitrogen of the air.

Air consists of 21 per cent oxygen and 79 per Y cent nitrogen (and argon) If the air be replaced by Vthe corresponding amount of oxygen as such the action becomes too violent and the flame too short to afford the -necessary time for reaction. With pure oxygen localized high tem eratures develop and the bauxite (and particularl impurepgrades containing much silica an iron) may sinter or agglomerate and lose its fine grained form.

I have found that the actions may be so con- Itrolled as to give a projected flame of convenient length with complete, or substantially complete utilization of the bauxite, and of the chlorin, if the oxygen used be diluted with some nitrogen; the amount of nitrogen however being less than that'normal to air. A small amount of diluting nitrogen regulates the deveolpment of heat without slowing it down unduly. I do not desire to have a ratio of nitrogen to oxygen more than 50:50, and in practice sometimes a ratio of 20 :8O is considerably better. Very frequently I use a mixture of equal volumes of air and of oxygen y which gives me a nitrogen oxygen ratlo .of

40 :60 and this works very well.

Using the oxygen diluted with nitrogen within the ranges mentioned I -have found action 'vm great capacity in the apparatus. Since il actions take place in suspension, the

walls of the apparatus ma be cooled and the life of linings prolonge indefinitely. At 1400 or 1500 F. the conjoint action of chlorin and carbon on firebrick is slow and at lower temperatures it disappears. With unl-diluted oxygen higher temperatures and quicker reactions are obtained but ordinarily in a flame of bauxite and carbon burning in a jet of chlorine mixed with pure oxygen to give aluminum chloride and oxides of carbon, the temperatures are locally too high and the action of the gases too rapid to permit complete utilization of the bauxite, especially if sinterin occurs. There is apt to be a loss of baumte as incompletely consumed granules, no matter how ne the bauxite is ground. Unconsumed bauxite goes forward as a dust; sometimesl of almost fume hneness. The finer the bauxite is ground, the less diculty there is in the use of pure oxygen and with baum'te ground extremely fine, the use of pure oxygen is worthwhile, since it gives enormous capacity for a given size of apparatus.r

Ordinarily however, as stated, I ndit better tov dilute the oxygen somewhat with nitrogen, as the grinding of the baumfte thereby becomes more economical. it is not necessary to grind to such extreme neness as with pure oxygen. In using bauxite of an ordinary degree of hneness, say, so that 7 0 or 80 per cent will go through a 100 mesh sieve, and-with coke of corresponding iineness, it is in general advisable to use the oxygen :nitrogen ratios stated.

With such a mixture of oxygen and nitrogen, n with chlorin to form a com'- ound"jet,'this jet projecting a mixture of ot bauxite and hot carbon into a reaction chamber, a true ame may be obtained in which bauxiteand chlorin completel disappear; so that a maximum utilization of both is obtained. The products ofcombustion leaving the iiame are a clean mixture of the va rs of aluminum chloride ca g some silicon chloride, iron chloride and titanium chloride with CO and CO2. I ordinarily adjust the amount of oxygen relative to the carbon, chlorin and bauxite, so as to obtain about equal volumes of CO and CO2. Gener- -ally, I usecxygen and chlorin in a'volume ratio of about 1:3.3. .advantageous ratios for the oxygen, chlorin and nitro n are therefore about 20 :67 :13 arts by vo ume.

I regard nitrogen as t e best diluent for the oxygen in the present invention, but other inert gases may be used in its lieu. For example, products of combustion or'the gases comin from the condensers used for condensing t e aluminum chloride may be 5 employed. In using either products of I,Icombustion or these tail gases, the proportion should be less than where nitrogen itself is used, since the contained CO2 exhibits a s ecic chemical cooling action. In using products of combustion or tail gases, they should be as free of H2O, or hydrogen as possible.-

. In producing a mixture of oxygen diluted with nitrogen, .either air or nitrogen itself can be used for admixture with the oxygen. The important oint is the ratio between 02 and N2 and t ey source is less important. In this connection, however, it may be noted that where air is used, it is best to dry it first and particularly in wet climates. Oxygen delivered from an air liquefying plant, the usual commercial source, is absolutel dry. Such a plant also delivers absolutely ry nitrogen and this nitrogen is convenient for use in the resent process. Unlike air, it requires no l ying.

I regard the resent invention as covering high speed reduction of anhydrous aluminum chlori e from bauxite or other form of alumina and carbon (advantageously oil coke) burning in aerial suspension in a mixture of chlorin and somewhat diluted oxygen, the dilution being such asto give the necessary time factor for the consumption of baux-v ite granules in convenient size without lowering the tem rature too much. The function of the d1 nent gas is, so to speak, that of lengthening aerial suspension a convenient one, although the suspensioilxof the ame is actually in an atmosphere of a mixture of vapors'of aluminum chloride and carbon oxids. The bauxite and the coke should be heated to free them ofmoisture and volatiles; and it is de,- si'rable to deliverthe mixture to the reaction zone at a high'temperature; say, l100'F. At this temperature the carbon ignites at once and the development of iame is normal.

In the accompanying drawing I have shown one lform of apparatus useful in. the

performance of my process. The view is a.v

section through the apparatus, certain parts being shown in elevation. The reaction chamber may be used in either a vertical or a horizontal position. As shown, it is horizontal. The reaction chamber l of tile, brick or other heat resisting material is provided at one end withan inlet 2 to which is connected a` feeding device 3 consisting of a main the operation itself, is admitted through the valved inlet 11.

At the other end, the reaction chamber is provided with an outlet 12 connecting with the trap 13 having a removable door 14 for removing yfrom time to time any settled dust which may pass the reaction chamber and the trap 13 is open at the top and is in communication with an aluminum chloride condenser (not shown). f

In a specific embodiment of my invention bauxite and petroleum coke are ground so that 70 or 80 per cent will pass a hundred mesh sieve and are fed continuously as a hot admixture by means of the hopper arrangement described to the inlet 2 while a mixture of oxygen and chlorin in the ratio of 1 :3.3 is

forced under pressure through the inlet 2. At the same time nitrogen or air is fed to the inlet by means of pipe 11 to give a ratio of 40 parts nitrogen to 60 of oxygen. ThisV v makes a compound jet and is projected into the reaction chamber carrying the freely re' acting bauxite and coke with it, forming what,

is virtually a flame. Within this flame, using the proportions specified there is/given the necessary time factor for complete consumption of the bauxite and complete utilization of chlorin where bauxite and chlorin are properly proportioned. y

As stated instead of using nitrogen some carbon dioxid may be used or the waste gases from the aluminum chloride condenser may be returned and admitted -through the pipe 11. The bauxite and coke are supplied from retort or oven in which they have been heated to a temperature suffieientto` drive out all moisture and volatiles. They are' then delivered t0 the reactioncharnbe-atusu'ally not less than 1100 F. With'the bauxite and coke at such a. temperatureignitionis 'instantaneous when vthe o gen and chlorin fcome in contact with the mixed solids.

.way of performing the process. The

The example given is illustrative "offu one nction of the oxygen in the flame is of course to develop heat at the expense of some'ofvthe carbon. As stated, however, the action of oxygen itself is a t to be local and violent with production o a short fla-me and incomplete reaction unless great care be exercised m grinding and in the rest of the o eration. With the oxygen somewhat dilute within the limits specified, the whole action becomes quite regular. In starting with the apparatus cold it is commonly necessary to use the oxygen somewhat stronger than in the later stages of operation afterl reaction chamber 1 is hot. And Ysometimes for one reason or another it A:s necessaryto vary the oxygen sup- What I claim is a l. In the manufacture of aluminum chloride, the process which comprises projecting a burning fine grained mixture of carbon and. bauxite by a jet of chlorin containing some 4tion with complete control of the operation.

oxygen, the said oxygen being accompanied 4 sby some nitrogen but not in amount greater than its` own volume.

2. In the manufacture of aluminum chlovao ride, the processywhich comprises projecting a fine grained hot mixture of aluminous matcriai and carbon by a jetof chlorin admixed with sufiicient oxygen to establish and maintain a temperature in the jet around 2000 F. said oxygen containing just enough nitrogen to prevent irregular and violent action; said nitrogen not being present in greater volume than the oxygen.

3. In the manufacture of aluminum chlo-.. ride, the process which comprises projecting a burning fine grained mixture of aluminous material and carbonby a jet of chlorin containing some oxygen and some nitrogen, the proportion of nitrogen -to oxygen being in about the ratio 40 60.

v4.v In the manufacture of aluminum chlo-- ride, the process which comprises burning a jet of finely divided aluminous and carbonaceous material inanatmosphereof gases. comprising oxygen, chlorin and nitrogen, the said gases being in the approximate ratios by volume of 2O :.67 :13.

5. In themanufacture of aluminum chloride, the process which comprises burning a jet of mixed aluminous and carbonaceous material, of a fineness such that 70 to 80 per cent pa'sses a 100 mesh sieve, in an atmosphere con.

taining chlorin, oxygen and nitro en; the 

